I really can’t grasp the concept of waves. I can imagine it a bit for sound waves: a speaker has a surface that pushes air, and the moving air eventually pushes the membrane in our ears.
But I’m confused about wifi etc. What exactly is the thing that physically travels? Is it air or something else? Does it physically move in a wavy pattern?
Edit: thanks for all the answers! But damn I’m overwhelmed. It’s gonna take me days to read and fully understand the answers. But thanks!
In: 87
Have you seen people doing ‘la ola’ in stadium ?
Where everybody stands up then sits down in turns. We cannot really say that any person physically moved. But something happened.
It is the information that moved, (and physicist will call that the perturbation from the initial state) and it has properties.
That’s what a wave is. Now you know what a disturbance in the force might feel like.
Have you seen people doing ‘la ola’ in stadium ?
Where everybody stands up then sits down in turns. We cannot really say that any person physically moved. But something happened.
It is the information that moved, (and physicist will call that the perturbation from the initial state) and it has properties.
That’s what a wave is. Now you know what a disturbance in the force might feel like.
Have you seen people doing ‘la ola’ in stadium ?
Where everybody stands up then sits down in turns. We cannot really say that any person physically moved. But something happened.
It is the information that moved, (and physicist will call that the perturbation from the initial state) and it has properties.
That’s what a wave is. Now you know what a disturbance in the force might feel like.
A wave is a periodic disturbance in… something.
I’ll take three cases, getting less intuitive as we go.
In **water waves**, the disturbance (in… water) is at right-angles to the wave’s direction of travel.
In **sound waves**, the disturbance is a pressure wave – periodic compression in the packing of the constituent particles of some medium (air, water, solids) where the disturbance is in the same direction as the wave’s direction of travel. (The usual analogy is to a Slinky being pushed to get a compression in the coils travelling along the toy’s length.)
WiFi signals travel in radio waves. These are an example of **electromagnetic waves**. In these waves (which also include light, microwaves etc.) things get less intuitive, because we’re no longer talking about a disturbance in a physical medium; we’re now talking about a disturbance in paired electric and magnetic fields. These fields in a sense feed off each other and keep themselves going in a straight line; they don’t need any medium in which to travel.
A wave is a periodic disturbance in… something.
I’ll take three cases, getting less intuitive as we go.
In **water waves**, the disturbance (in… water) is at right-angles to the wave’s direction of travel.
In **sound waves**, the disturbance is a pressure wave – periodic compression in the packing of the constituent particles of some medium (air, water, solids) where the disturbance is in the same direction as the wave’s direction of travel. (The usual analogy is to a Slinky being pushed to get a compression in the coils travelling along the toy’s length.)
WiFi signals travel in radio waves. These are an example of **electromagnetic waves**. In these waves (which also include light, microwaves etc.) things get less intuitive, because we’re no longer talking about a disturbance in a physical medium; we’re now talking about a disturbance in paired electric and magnetic fields. These fields in a sense feed off each other and keep themselves going in a straight line; they don’t need any medium in which to travel.
A wave is a periodic disturbance in… something.
I’ll take three cases, getting less intuitive as we go.
In **water waves**, the disturbance (in… water) is at right-angles to the wave’s direction of travel.
In **sound waves**, the disturbance is a pressure wave – periodic compression in the packing of the constituent particles of some medium (air, water, solids) where the disturbance is in the same direction as the wave’s direction of travel. (The usual analogy is to a Slinky being pushed to get a compression in the coils travelling along the toy’s length.)
WiFi signals travel in radio waves. These are an example of **electromagnetic waves**. In these waves (which also include light, microwaves etc.) things get less intuitive, because we’re no longer talking about a disturbance in a physical medium; we’re now talking about a disturbance in paired electric and magnetic fields. These fields in a sense feed off each other and keep themselves going in a straight line; they don’t need any medium in which to travel.
If you’ve played with magnets, you know that (for example) the North pole of one magnet has a region of space close to it that will repel the North pole of another magnet. This “magnetic field” is stronger, closer to the magnet.
A related thing happens in the experiment you might have seen, where someone (on an electrically insulated pad!) touches a high-voltage machine and their hair stands up. Similar charges on different strands of hair repel each other. This is called an “electric field”, and it’s stronger closer to the charges — often electrons in everyday situations.
Now these two fields are directly related to each other, because a *changing* magnetic field will create an electric field, and vice versa. A guy named Maxwell figured out a set of equations for this. One thing that popped out of the equations was that you could play with the numbers and come up with a velocity, the speed of light, which has been experimentally verified. So changes to these fields are key to how they relate, and the changes travel at the speed of light.
Now if you put an Alternating Current on an wire not connected on the other end (aka an antenna), the electric charges first try to rush in, and kind of bunch up at the end of the wire in a subatomic traffic jam. The moving electrons make a magnetic field. Bunched up electrons make an electric field. Since the current is alternating, it’s constantly changing and in fact reversing. So as the electrons flow away from the end of the wire, the electric field gets less intense–and this change in the electric field travels away from the wire at the speed of light. At the same time, the magnetic field reverses, and this change also flies away from the wire at the speed of light.
So off through space goes this changing magnetic field, which recreates a changing electric field, which recreates a changing magnetic field, which recreates …
And for certain frequencies, you call this disturbance a radio wave–or for higher frequencies, light, or X-Rays, etc.
If you’ve played with magnets, you know that (for example) the North pole of one magnet has a region of space close to it that will repel the North pole of another magnet. This “magnetic field” is stronger, closer to the magnet.
A related thing happens in the experiment you might have seen, where someone (on an electrically insulated pad!) touches a high-voltage machine and their hair stands up. Similar charges on different strands of hair repel each other. This is called an “electric field”, and it’s stronger closer to the charges — often electrons in everyday situations.
Now these two fields are directly related to each other, because a *changing* magnetic field will create an electric field, and vice versa. A guy named Maxwell figured out a set of equations for this. One thing that popped out of the equations was that you could play with the numbers and come up with a velocity, the speed of light, which has been experimentally verified. So changes to these fields are key to how they relate, and the changes travel at the speed of light.
Now if you put an Alternating Current on an wire not connected on the other end (aka an antenna), the electric charges first try to rush in, and kind of bunch up at the end of the wire in a subatomic traffic jam. The moving electrons make a magnetic field. Bunched up electrons make an electric field. Since the current is alternating, it’s constantly changing and in fact reversing. So as the electrons flow away from the end of the wire, the electric field gets less intense–and this change in the electric field travels away from the wire at the speed of light. At the same time, the magnetic field reverses, and this change also flies away from the wire at the speed of light.
So off through space goes this changing magnetic field, which recreates a changing electric field, which recreates a changing magnetic field, which recreates …
And for certain frequencies, you call this disturbance a radio wave–or for higher frequencies, light, or X-Rays, etc.
If you’ve played with magnets, you know that (for example) the North pole of one magnet has a region of space close to it that will repel the North pole of another magnet. This “magnetic field” is stronger, closer to the magnet.
A related thing happens in the experiment you might have seen, where someone (on an electrically insulated pad!) touches a high-voltage machine and their hair stands up. Similar charges on different strands of hair repel each other. This is called an “electric field”, and it’s stronger closer to the charges — often electrons in everyday situations.
Now these two fields are directly related to each other, because a *changing* magnetic field will create an electric field, and vice versa. A guy named Maxwell figured out a set of equations for this. One thing that popped out of the equations was that you could play with the numbers and come up with a velocity, the speed of light, which has been experimentally verified. So changes to these fields are key to how they relate, and the changes travel at the speed of light.
Now if you put an Alternating Current on an wire not connected on the other end (aka an antenna), the electric charges first try to rush in, and kind of bunch up at the end of the wire in a subatomic traffic jam. The moving electrons make a magnetic field. Bunched up electrons make an electric field. Since the current is alternating, it’s constantly changing and in fact reversing. So as the electrons flow away from the end of the wire, the electric field gets less intense–and this change in the electric field travels away from the wire at the speed of light. At the same time, the magnetic field reverses, and this change also flies away from the wire at the speed of light.
So off through space goes this changing magnetic field, which recreates a changing electric field, which recreates a changing magnetic field, which recreates …
And for certain frequencies, you call this disturbance a radio wave–or for higher frequencies, light, or X-Rays, etc.
A wave is any thing that changes the average. Like the ocean is still until wind blows and it creates a wave, moving water up and down towards a direction. Light, radio, gamma, Wi-Fi, UV, Bluetooth etc. are all part of the electromagnetic spectrum. Which is, to simplify, a wave that has its own energy packets called photons. So depending on the frequency of the wave, they can either be massive, like radio waves, or small like gamma. Wi-fi, which is a microwave is in between. So when moving in the physical space, a larger wave would have more interference (like when you turn on a radio and you hear the fuzz or how old TVs had noise) but but since its a low frequency wave, it carries less energy. On the flip side, a higher frequency would carry more energy and information but for a shorter range before it becomes a longer wave then interference becomes are problem. (Interference can be anything…for radio it can be a mountain, particles in the wind, humidity etc. for microwaves it can be a thick wall, a person etc. also the waves are small so they can go in between atoms and their energy level is low enough that it doesn’t affect atomic structures.
Also the thing that travels is a photon when you look close, but its a wave when you zoom out. Wave-particle duality did a number to a lot of physicists. Also! It doesn’t need a medium. The wave moves faster in a vacuum.
(A photon is a massless particle that is a unit of energy. And it moves at the speed of light (which is also a photon).
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